Separator having porous coating layer and electrochemical device containing the same

1. A separator, comprising:

(A) a porous substrate having a plurality of pores; and

(B) a porous coating layer formed on at least one surface of the porous substrate to have a thickness of 0.01 to 20 μm and made of a mixture of a plurality of inorganic particles with a particle size of 0.001 to 10 μm and a binder polymer,

wherein a weight ratio of the inorganic particles to the binder polymer is 50:50 to 99:1,

wherein the binder polymer comprises:

(i) polyvinylidene fluoride-co-hexafluoropropylene which is a first polyvinylidene fluoride-based copolymer having solubility of 25 weight % or more with respect to acetone at 35° C.;

(ii) polyvinylidene fluoride-co-chlorotrifluoroethylene which is a second polyvinylidene fluoride-based copolymer having solubility of 10 weight % or less with respect to acetone at 35° C.; and

(iii) a polymer having a cyano group; and

wherein, based on the entire weight of the porous coating layer, the content of the first polyvinylidene fluoride-based copolymer is 5 to 30 weight %, the content of the second polyvinylidene fluoride-based copolymer is 1 to 10 weight %, and the content of the polymer having a cyano group is 0.1 to 5 weight %, respectively.

2. The separator according to claim 1 ,

wherein the polymer having a cyano group is at least one selected from the group consisting of cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, and their mixtures.

3. The separator according to claim 1 ,

wherein the inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or above, inorganic particles having lithium-ion transferring capability, and their mixtures.

4. The separator according to claim 3 ,

wherein the inorganic particle having a dielectric constant of or above is an inorganic particle selected from the group consisting of BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB(Mg 3 Nb 2/3 )O 3 —PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al 2 O 3 , SiC, TiO 2 , and their mixtures.

5. The separator according to claim 3 ,

wherein the inorganic particle having lithium ion transferring capability is an inorganic particle selected from the group consisting of lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y type glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO 3 , 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P x S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitrides (Li x N y , 0<x<4, 0<y<2), SiS 2 (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4) type glass, P 2 S 5 (Li x P y S z , 0<x<3, 0<y<3, 0<z<7) type glass, and their mixtures.

6. The separator according to claim 1 ,

wherein the porous substrate is a polyolefin-based porous substrate.

7. The separator according to claim 6 ,

wherein the polyolefin-based porous substrate is made of any one polymer selected from the group consisting of polyethylene, polypropylene, polybutylene, polypentene, and their mixtures.

8. An electrochemical device, comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode,

wherein the separator is a separator defined in claim 1 .

9. The electrochemical device according to claim 8 ,

wherein the electrochemical device is a lithium secondary battery.